93 Lumina Rear Disk Brakes

[SpinnerCee]

Attempting to simply replace the rear disk pads and rotor (they wore down to rivets) on a friend's car has proven to be quite an exercise.

Starting on the most damaged side -- removing the caliper was so simple (two bolts) -- the problem was returning the caliper piston (pushing it in) so the new pads would fit over the new rotor -- The usual method of a c-clamp over the piston, broke a perfectly good aluminum C-clamp! -- so i then asumed that the caliper was "Frozen" (not likely, since it was still tearing up the old rotor under braking only) -- so I bought a replacement caliper -- at the shop someone mentioned that there is a tool that must be used to "screw" the caliper back in because it "ratchets" out as the pads wear to take up the slack, and maybe compensate for the parking brake (which is mouted to the caliper)?

Anyone have any experience with this monster? Where could the tool be found? Is a caliper replacement part of the brake service procedure?

Also, the replacement caliper seems to have excessive play between the pads and the rotor -- is there also another procedure to get the initial clearance, or is it all automatic. The car has ABS, and right now, the car has virtually no braking at all, even after bleeding the replaced caliper.

How many other models have the same rear disk brake assembly? I guess it's a choice of the cost of the tool over the cost of a caliper -- but if the tool can be used on other models it would be worth the cost.....

Any info would be helpful -- Chris

[richtazz]

The tool is cheap, and is available at Auto-Zone, Advance, CSK, etc... IT looks like a little block with 6 different sides. The tool is driven with a 3/8 ratchet, and has the different sides so it can be used for multiple vehicles.

[Manny_boy]

91-95 have the same rear brake system. You don't have to have the special tool, you just have to have a pair of needle nose pliers. You have to twist the rear caliper in. It will help if you remove the parking brake tang (nut and all, it will relieve some of the pressure during your caliper bottoming operation. Once you re-install the parking brake tang, if you pump it with a pair of pliers, the excessive clearance between the pad and rotor will be gone. The book says to pump the parking brake to seat the pads, but if that lum is like most 91-95, its frozen.

Caliper replacement is not necessarily part of the procedure, but the factory calipers have a defect. The steel sliders freeze if not properly maintained (lube and seal). Remanufactured calipers have taken care of this issue, the sliders are brass (blue in color). Before I replaced my rear calipers, I used to remove them from the car, push out the sliders, clean the bore with a brake hone, clean the sliders with emery cloth, re-lube and check the boots, whenever I changed pads, as routine maintenence.

If you haven't already, have your friend invest in a Chilton/Haynes manual for that car. *Priceless*

[Manny_boy]

Sorry Richtazz, you must have posted while I was typing - not trying to step on your toes... hmmm... I need to get one of those, I'm sure its easier than using needlenose.

[maxwedge]

The key to doing these rr calipers is applying inward pressure as the piston is turned, there is a " real" special tool that does both at the same time, Matco Napa, Snap on.

[richtazz]

No problem Manny, there is nothing wrong with giving an alternative method that doesn't require special tools. I've done them your way too. The tool is so cheap, it just makes it easier. Sometimes trying to hold the needle nose spread just right while pushing and turning can result in scraped knuckles and many swear words. I think I paid $4-$5 bucks for my tool, and while the Lumi's are easy with the plier trick, I've used it on other folks non-GM cars, and it proved priceless. Good tip on the slider issue too, I should have mentioned it myself.

[comptech_69]

The tool definately makes your life much easier. I just did this to my car about a month ago. After you have the brakes on the car, what you want to do is set the e-brake and release it a whole bunch of times. This adjusts the rear brakes so they actually work. I set and released the parking brake about 20 times on my car, and after that they worked great.

[LMP]

[quote=Manny_boy]...you just have to twist the rear caliper in. It will help if you remove the parking brake tang ....QUOTE]
yes..2 years later but really useful.....thanks for the hint...I just wondered why the piston could not be pushed in with my son'"s Z-34 . I did have to remove the parking brake lever from the caliper and only then the action of turning the piston would pull the parking axle in and then the piston could be pushed in...with the parking axle then regaining its position out. ON the first side, i pulled the parking brake axle in too much all in one shot and brake fluid escaped as the axle was too much in and quit the seal..but then on the second side, I did it bit by bit...
probably this tool that "pushes as it turns" would make things easier..but i did not have the time to look for that

[sad-lumina-owner]

Yep.

I (luckily) couldn't even get the pads to clip on, so I took the (new) caliper back to CanTire where I got it and the pads.

The mechanic laughed at the idea of me trying to turn in the piston with needlenose pliers (I just wrecked my pliers).

He brought out the REAL tool ($40 from GM) that has a 'key' with four poles and a screwlike clamp (like half a c-clamp with an extra threaded piece).

He turned the piston just right (it has to be square and flush), like a cross.

Then the pads clipped on right.

He also described 'jacking' the emergency brake with a screwdriver, but this actually had no discernable effect at all toward tightening up the brakes.

Again, if you can't adjust the emergency brake (say like mine the adjustment screw on the cable is rusted out) then they aren't going to work properly.
New cable seems the only real answer there.

Pumping the brakes? I did that as a matter of course when bleeding caliper, and brakes work well enough.

My future strategy for when I replace the other rear caliper is just to talk the mechanic where I buy the thing into setting it up before I go home and begin the install.

I have one obvious question:

CAN YOU replace this style of disc brake caliper with a different one, say with the dual pistons that can EASILY be set up with a c-clamp?

Why are we struggling with a shitty design of caliper when other years and makes don't have to do this? I am wondering if the spacing/threads for the mounting bolts is the same for ALL GMs here.

Why not just use a nicer caliper, like those on the front!!!!?

ANd while we're at it, why not replace the stupid torx bolts on the front with ordinary bolts like those found on the rear?

With those two items swapped out, doing brakes on the Lumina would be a cinch!!!